1. Field of the Invention
The invention in general relates to a towed body lauching and retrieval arrangement, and particularly to one which fits into a limited space.
2. Description of the Prior Art
In copending application Ser. No. 588,594 filed Mar. 12, 1984 and assigned to the same assignee as the present invention, a towed body deployment/retrieval system is described wherein the requirement for a conventional tow boom-carried sheave is eliminated.
The system described includes a first hollow arm with a sheave member rotatable about an axle which is disposed below the arm. A second hollow arm is mechanically coupled to the axle and is rotatable about the sheave member between a first position in which the arms are horizontally aligned, and a second position wherein second arm is vertical.
A cable wound upon a winch extends through the first arm, over the sheave, and through the second arm for connection to the towed body.
The previously described arrangement is extremely suitable for not only surface vessels for providing a low center of gravity system, but for other carriers which have a height restriction, such as the helicopter described in the aforementioned copending application.
The cable which is utilized is of a certain strength and diameter compatible with the tow requirements. If a particular mission requires the use of a heavier tow cable, then a greater diameter sheave is dictated. This is due to the fact that the life of the cable depends not only upon the number of deployment/retrieval cycles, but also upon how severe a bend the cable makes over the sheave. The radius of curvature of the sheave should be as large as possible to prolong the cable life.
Due to the limited height requirement, the sheave diameter of the previously described system is limited. The present invention provides a similar retrieval/deployment system which can use a heavier cable over an effectively increased radius of curvature sheave in the same space requirement as the previous system.